Especially in high voltage systems, it is often necessary to transfer information in the form of electric signals, from a low side to a high side of an electric circuit, where in the low side of the circuit signals are related to a first electric potential (e.g., ground potential) and in the high side of the circuit signals are related to a second electric potential (e.g., a floating reference potential). One example is a high side semiconductor switch whose switching state is to be controlled by a control signal. The voltage level of the control signal in this case is not related to a fixed potential (further referred to as ground potential, but not limited to a ground potential), but with respect to the potential of a circuit-node common to the switch and the load. That is, the voltage level of the control signal is related to a floating reference potential that depends on the switching state of the high side semiconductor switch.
Critical parameters for level-shifters are power consumption, delay time, and noise robustness. In view of power consumption DC level-shifters can be very efficient, because power is only dissipated during switching operation of the level shifter, i.e., during the transmission from one logic level to another logic level. Concerning noise robustness it is expected that level-shifters do not erroneously change their state due to noise and parasitic inductive or capacitive coupling (i.e., cross-talk).
Level shifters of this kind conventionally have an input stage receiving an input signal to be level-shifted, a limiter stage receiving a floating reference potential which usually is the potential of the switched circuit-note mentioned above, and an output stage providing an output signal which is substantially a level-shifted (or inverted and level-shifted) version of the input signal.
The delay between the input and the output signal caused by the level-shifter is due to the charging and the discharging of parasitic capacitors in the input stage. The capacitance values of these parasitic capacitors can not directly be influenced by circuit design.